Identification of wortmannin-sensitive targets in 3T3-L1 adipocytes - Dissociation of insulin-stimulated glucose uptake and GLUT4 translocation
Identification of wortmannin-sensitive targets in 3T3-L1 adipocytes - Dissociation of insulin-stimulated glucose uptake and GLUT4 translocation
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DOI：
10.1074/jbc.274.35.24677
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发表时间：
1999-08-27
影响因子：
4.8
通讯作者：
Birnbaum, MJ
中科院分区：
文献类型：
--
作者：
Hausdorff, SF;Fingar, DC;Birnbaum, MJ
目前的研究探讨了磷脂酰肌醇3-激酶(PI3-Kinase)亚型在胰岛素刺激的葡萄糖摄取和葡萄糖转运蛋白4(GLUT4)易位中的作用，通过显微注射针对I类PI3-激酶p110催化亚基的抗体的实验表明，在GLUT4易位中绝对需要这种形式的酶。这一发现得到了PI3-激酶拮抗剂Wortmannin抑制GLUT4和胰岛素反应性氨基肽酶转位的证实，其剂量效应与抑制另一类PI3-激酶依赖事件所需的剂量反应相同。有趣的是，Wortmannin以低得多的剂量抑制胰岛素刺激的葡萄糖摄取，这表明该药物存在第二个更高亲和力的靶点。随后从培养液中去除Wortmannin将这一量效曲线移动到类似于GLUT4转位和pp70 SG-Kinase的量效曲线，这与低亲和力靶点p110是一致的，p110被Wortmannin不可逆地抑制，Wortmannin没有减少稳定表达Myr-Akt的细胞对葡萄糖的摄取，从而结构性地诱导GLUT4转位到质膜；这表明Wortmannin不直接抑制转运蛋白。除了阐明3T3-L1脂肪细胞的第二个Wortmannin敏感途径外，这些研究还表明，质膜上GLUT4的存在不足以激活葡萄糖摄取。
The current studies investigated the contribution of phosphatidylinositol 3-kinase (PI3-kinase) isoforms to insulin-stimulated glucose uptake and glucose transporter 4 (GLUT4) translocation, Experiments involving the microinjection of antibodies specific for the p110 catalytic subunit of class I PI3-kinases demonstrated an absolute requirement for this form of the enzyme in GLUT4 translocation. This finding was confirmed by the demonstration that the PI3-kinase antagonist wortmannin inhibits GLUT4 and insulin-responsive aminopeptidase translocation with a dose response identical to that required to inhibit another class I PI3-kinase-dependent event, activation of pp70 SG-kinase, Interestingly, wortmannin inhibited insulin-stimulated glucose uptake at much lower doses, suggesting the existence of a second, higher affinity target of the drug. Subsequent removal of wortmannin from the media shifted this dose-response curve to one resembling that for GLUT4 translocation and pp70 SG-kinase, This is consistent with the lower affinity target being p110, which is irreversibly inhibited by wortmannin, Wortmannin did not reduce glucose uptake in cells stably expressing Myr-Akt, which constitutively induced GLUT4 translocation to the plasma membrane; this demonstrates that wortmannin does not inhibit the transporters directly. In addition to elucidating a second wortmannin-sensitive pathway in 3T3-L1 adipocytes, these studies suggest that the presence of GLUT4 on the plasma membrane is not sufficient for activation of glucose uptake.